Power distribution network evaluation method and system based on zero-sequence current feature extraction
Through the method based on zero-sequence current feature extraction, the problem of high labor intensity of traditional distribution network fault positioning methods is solved, and more efficient and accurate fault positioning is achieved, which meets the needs of complex environments of modern distribution networks.
Patent Information
- Application Number
- CN202411683569.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-02-28
AI Technical Summary
Traditional distribution network fault positioning methods are labor-intensive and difficult to adapt to current production needs, especially in complex grids and severe weather conditions.
The distribution network evaluation method based on zero-sequence current feature extraction is adopted. By obtaining the bus voltage and zero-sequence current, wavelet multi-resolution decomposition is performed, transient characteristic signals are extracted, and the non-power frequency energy and energy ratios are calculated to locate the faulty line.
It improves the accuracy and efficiency of fault positioning, reduces manpower and material consumption, and adapts to the needs of complex grids and harsh environments of modern distribution networks.
Smart Images
Figure CN119535098A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of distribution network evaluation, and in particular to a distribution network evaluation method and system based on zero-sequence current feature extraction. Background Art
[0002] At present, most distribution networks use a neutral point non-effective grounding system, and single-phase grounding faults account for more than 80% of the total faults. When a single-phase to ground short-circuit fault occurs, since there is no electrical connection between the earth and the neutral point or a reactor is connected in series, the short-circuit current is very small and the protection device does not need to trip immediately, thereby improving the reliability of system operation.
[0003] It is also because the installed arc suppression coil makes the system single-phase grounding short-circuit current very small, and the voltage and current amplitude and phase angle on the fault line and the non-fault line are not much different, making it difficult to determine the location of the fault. However, with the increase of feeders and the increase of capacitive current, it is easy to change from single-phase grounding to multi-point grounding short circuit during long-term operation. Arc grounding will also cause overvoltage in the system, damage equipment, and destroy the safe operation of the system. Therefore, it is necessary to find the fault line and fault location in time. In order to improve the reliability of power supply and reduce the impact of power outages caused by power grid failures, power supply companies in various countries are actively implementing distribution operation automation technology. Through real-time monitoring, hidden dangers are discovered in time to avoid accidents, and faults are automatically located, isolated, and power supply is restored to non-fault lines to reduce the power outage time. Single-phase grounding short circuit is the short-circuit fault type with the highest probability of occurrence. How to find the location of the fault in a timely and accurate manner after a single-phase grounding fault occurs in the distribution network, isolate the fault area, and restore normal power supply to the non-fault area is an important purpose of the current research on single-phase grounding faults in distribution networks.
[0004] As the distribution network structure is strengthened, the number of branch lines has also increased. It is very difficult to find the location of the specific faulty line using traditional line inspection methods. This not only consumes a lot of manpower and material resources, but also prolongs the power outage time and affects the reliability of power supply, especially in cold winter or rainy and snowy weather and difficult road conditions. The existing methods of finding faulty lines are very labor-intensive and difficult to adapt to current production requirements. Summary of the invention
[0005] Based on this, the purpose of the present invention is to propose a distribution network evaluation method and system based on zero-sequence current feature extraction, aiming to solve the problem that the traditional technology uses line patrol to determine the fault line of the distribution network, which is labor-intensive and difficult to adapt to current production needs.
[0006] In a first aspect, an embodiment of the present invention provides a distribution network evaluation method based on zero-sequence current feature extraction, the method comprising: Obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection conditions are met according to the bus voltage; If the preset line selection conditions are met, the zero-sequence current of each outgoing line is decomposed by wavelet multi-resolution and a transient characteristic signal is extracted, wherein the transient characteristic signal includes a DC signal component, an industrial frequency signal component and a high-frequency oscillation component; Acquire the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; Traversing the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; It is determined whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a faulty line.
[0007] In some embodiments, the step of obtaining the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component includes: Accumulating and reconstructing the DC signal component and the high-frequency oscillation component to obtain a non-industrial frequency signal; The non-power frequency signal is subjected to Hilbert transformation to obtain the instantaneous amplitude of the non-power frequency signal, and the non-power frequency energy of the non-power frequency signal is calculated according to the instantaneous amplitude.
[0008] In some embodiments, the step of performing Hilbert transform on the non-power frequency signal to obtain the instantaneous amplitude of the non-power frequency signal, and calculating the non-power frequency energy of the non-power frequency signal according to the instantaneous amplitude includes: The non-power frequency energy is obtained according to the following formula: Among them, E i represents the non-power frequency energy of the i-th line, k represents the number of sampling times of the same line, f(j) represents the instantaneous amplitude when the zero-sequence current is collected for the jth time, and α represents a constant.
[0009] In some embodiments, the step of performing Hilbert transform on the non-power frequency signal and traversing the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network includes: The energy proportion of each line's non-power frequency capacity is obtained according to the following formula: Among them, ω i It represents the energy proportion of the non-power frequency capacity of the i-th line, and m represents the total number of lines in the target distribution network.
[0010] In some embodiments, the step of obtaining the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and judging whether the preset line selection condition is met according to the bus voltage includes: Determining whether the bus voltage is greater than or equal to a first preset voltage threshold; If the bus voltage is greater than or equal to a first preset voltage threshold, it is determined that the preset line selection condition is met; If the bus voltage is less than the first preset voltage threshold, it is determined that the preset line selection condition is not met.
[0011] In some embodiments, the step of determining whether the bus voltage is greater than or equal to a first preset voltage threshold comprises: The judgment is made according to the following formula: U0≥βU N Among them, U0 represents the bus voltage, β represents a constant, which is 5%-15%, and U N Indicates the rated voltage of the busbar.
[0012] In a second aspect, an embodiment of the present invention further proposes a distribution network evaluation system based on zero-sequence current feature extraction, the system comprising: A zero-sequence current acquisition module is used to obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection condition is met according to the bus voltage; A signal extraction module is used to perform wavelet multi-resolution decomposition on the zero-sequence current of each outgoing line and extract transient characteristic signals if the preset line selection conditions are met. The transient characteristic signals include a DC signal component, an industrial frequency signal component, and a high-frequency oscillation component; An energy calculation module, used for obtaining the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; An energy ratio acquisition module is used to traverse the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; The fault line location module is used to determine whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a fault line.
[0013] In some embodiments, the signal extraction module is further configured to: Accumulating and reconstructing the DC signal component and the high-frequency oscillation component to obtain a non-industrial frequency signal; The non-power frequency signal is subjected to Hilbert transformation to obtain the instantaneous amplitude of the non-power frequency signal, and the non-power frequency energy of the non-power frequency signal is calculated according to the instantaneous amplitude.
[0014] In a third aspect, an embodiment of the present invention further provides a storage medium, including one or more programs stored in the storage medium, which, when executed, implements the distribution network evaluation method based on zero-sequence current feature extraction as described above.
[0015] In a fourth aspect, an embodiment of the present invention further provides an electronic device, the electronic device comprising a memory and a processor, wherein: The memory is used to store computer programs; When the processor is used to execute the computer program stored in the memory, the distribution network evaluation method based on zero-sequence current feature extraction as described above is implemented.
[0016] In summary, according to the above-mentioned distribution network evaluation method based on zero-sequence current feature extraction, the zero-sequence current of each outgoing line is decomposed by wavelet multi-resolution and the transient characteristic signal is extracted. Then, the extracted transient signal component is compared with the baseband signal (total non-industrial frequency signal) to obtain the proportion of transient signals. When the proportion is greater than a certain value, it indicates that the line operation state has undergone a sudden change, that is, a fault has occurred. At the same time, multiple wavelets are used for analysis, and the analysis results are comprehensively analyzed to improve the accuracy of the algorithm.
[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description or will be learned through embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 A flow chart of a distribution network evaluation method based on zero-sequence current feature extraction proposed in an embodiment of the present invention; Figure 2 It is a structural schematic diagram of a distribution network evaluation system based on zero-sequence current feature extraction in an embodiment of the present invention.
[0019] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION
[0020] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.
[0022] See also Figure 1 , which is a flow chart of a distribution network evaluation method based on zero-sequence current feature extraction in a first embodiment of the present invention, the method comprises steps S101 to S105, wherein: Step S101: Obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection condition is met according to the bus voltage; Before fault detection, in order to avoid wasting resources due to frequent detection when the distribution network is actually fault-free, a preliminary detection is first performed on the target distribution network to determine whether there is a fault in the target distribution network.
[0023] The specific process of determining whether the preset line selection conditions are met is: determine whether the bus voltage is greater than or equal to a first preset voltage threshold; if the bus voltage is greater than or equal to the first preset voltage threshold, determine that the preset line selection conditions are met; if the bus voltage is less than the first preset voltage threshold, determine that the preset line selection conditions are not met.
[0024] It should be pointed out that when it is determined that the preset line selection conditions are met, it means that a fault has occurred in the target distribution network.
[0025] In some embodiments, the judgment is made specifically according to the following formula: U0≥βU N Among them, U0 represents the bus voltage, β represents a constant, which is 5%-15%, and U N Indicates the rated voltage of the busbar.
[0026] Step S102: If the preset line selection conditions are met, the zero-sequence current of each outgoing line is subjected to wavelet multi-resolution decomposition and the transient characteristic signal is extracted, and the transient characteristic signal includes a DC signal component, an industrial frequency signal component, and a high-frequency oscillation component; it should be noted that in actual research, the applicant found that the DC component in the zero-sequence current signal is similar to and smaller than the industrial frequency component in frequency, while the frequency of the high-frequency oscillation component is higher and has a large difference from the frequency of the industrial frequency component. In order to meet the condition that the sum of the components of the signal after decomposition is the input signal, the center frequency is adaptively selected based on the spectrum. Therefore, the components obtained by one decomposition include a DC signal component, an industrial frequency signal component, and a high-frequency oscillation component.
[0027] Step S103: Obtain the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; it can be understood that the components decomposed except the power frequency signal component are all non-power frequency components. In order to obtain the non-power frequency energy, it is first necessary to perform cumulative reconstruction on the DC signal component and the high-frequency oscillation component to obtain the non-power frequency signal; then perform Hilbert transform on the non-power frequency signal to obtain the instantaneous amplitude of the non-power frequency signal, and calculate the non-power frequency energy of the non-power frequency signal according to the instantaneous amplitude.
[0028] Specifically, the non-power frequency energy is obtained according to the following formula: Among them, E i represents the non-power frequency energy of the i-th line, k represents the number of sampling times of the same line, f(j) represents the instantaneous amplitude when the zero-sequence current is collected for the jth time, and α represents a constant.
[0029] Step S104: traverse the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; It should be noted that when a single-phase grounding fault occurs, due to the sudden change of the non-power frequency component of the fault line, the energy of the non-power frequency component of the fault line accounts for a higher proportion of the non-power frequency components of all lines. Based on this, in order to accurately locate the fault line, the proportion of non-power frequency energy of each line is accurately calculated and screened, so that the fault line can be quickly located.
[0030] Specifically, the energy proportion of the non-power frequency capacity of each line is obtained according to the following formula: Among them, ω i It represents the energy proportion of the non-power frequency capacity of the i-th line, and m represents the total number of lines in the target distribution network.
[0031] Step S105: determine whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a faulty line.
[0032] It should be noted that the preset ratio threshold is determined based on the characteristics of faulty lines that have been detected in the past, and is not limited in detail in this embodiment. In actual situations, it can be obtained based on the lower limit of the energy ratio of a large number of known faulty lines.
[0033] It can be understood that if the energy ratio of the line is less than or equal to the preset ratio threshold, it means that the line is a normal line.
[0034] In summary, according to the above-mentioned distribution network evaluation method based on zero-sequence current feature extraction, the zero-sequence current of each outgoing line is decomposed by wavelet multi-resolution and the transient characteristic signal is extracted. Then, the extracted transient signal component is compared with the baseband signal (total non-industrial frequency signal) to obtain the proportion of transient signals. When the proportion is greater than a certain value, it indicates that the line operation state has undergone a sudden change, that is, a fault has occurred. At the same time, multiple wavelets are used for analysis, and the analysis results are comprehensively analyzed to improve the accuracy of the algorithm.
[0035] See also Figure 2 , which is a schematic diagram of the structure of a distribution network evaluation system based on zero-sequence current feature extraction in one embodiment, the system includes: The zero-sequence current acquisition module 10 is used to obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection condition is met according to the bus voltage; The signal extraction module 20 is used to perform wavelet multi-resolution decomposition on the zero-sequence current of each outgoing line and extract transient characteristic signals if the preset line selection conditions are met. The transient characteristic signals include a DC signal component, an industrial frequency signal component, and a high-frequency oscillation component. An energy calculation module 30 is used to obtain the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; an energy ratio acquisition module 40 is used to traverse the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; The fault line location module 50 is used to determine whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a fault line.
[0036] On the other hand, the present invention further proposes a computer storage medium on which one or more programs are stored, and when the programs are executed by a processor, the above-mentioned distribution network evaluation method based on zero-sequence current feature extraction is implemented.
[0037] On the other hand, the present invention further proposes an electronic device, including a memory and a processor, wherein the memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the above-mentioned distribution network evaluation method based on zero-sequence current feature extraction.
[0038] Those skilled in the art will appreciate that the logic and / or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For purposes of this specification, "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.
[0039] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.
[0040] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or a combination thereof: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.
[0041] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0042] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.
Claims
1. A distribution network evaluation method based on zero-sequence current feature extraction, characterized in that: The method comprises: Obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection conditions are met according to the bus voltage; If the preset line selection conditions are met, the zero-sequence current of each outgoing line is decomposed by wavelet multi-resolution and a transient characteristic signal is extracted, wherein the transient characteristic signal includes a DC signal component, an industrial frequency signal component and a high-frequency oscillation component; Acquire the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; Traversing the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; It is determined whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a faulty line.
2. The distribution network evaluation method based on zero-sequence current feature extraction according to claim 1 is characterized in that: The step of obtaining the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component comprises: Accumulating and reconstructing the DC signal component and the high-frequency oscillation component to obtain a non-industrial frequency signal; The non-power frequency signal is subjected to Hilbert transformation to obtain the instantaneous amplitude of the non-power frequency signal, and the non-power frequency energy of the non-power frequency signal is calculated according to the instantaneous amplitude.
3. The distribution network evaluation method based on zero-sequence current feature extraction according to claim 2 is characterized in that: The step of performing Hilbert transform on the non-power frequency signal to obtain the instantaneous amplitude of the non-power frequency signal, and calculating the non-power frequency energy of the non-power frequency signal according to the instantaneous amplitude comprises: The non-power frequency energy is obtained according to the following formula: Among them, E i represents the non-power frequency energy of the i-th line, k represents the number of sampling times of the same line, f(j) represents the instantaneous amplitude when the zero-sequence current is collected for the jth time, and α represents a constant.
4. The distribution network evaluation method based on zero-sequence current feature extraction according to claim 3 is characterized in that: The step of performing Hilbert transform on the non-power frequency signal and traversing the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network comprises: The energy proportion of each line's non-power frequency capacity is obtained according to the following formula: Among them, ω i It represents the energy proportion of the non-power frequency capacity of the i-th line, and m represents the total number of lines in the target distribution network.
5. The distribution network evaluation method based on zero-sequence current feature extraction according to claim 1 is characterized in that: The step of obtaining the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and judging whether the preset line selection condition is met according to the bus voltage includes: Determining whether the bus voltage is greater than or equal to a first preset voltage threshold; If the bus voltage is greater than or equal to a first preset voltage threshold, it is determined that the preset line selection condition is met; If the bus voltage is less than the first preset voltage threshold, it is determined that the preset line selection condition is not met.
6. The distribution network evaluation method based on zero-sequence current feature extraction according to claim 5 is characterized in that: The step of determining whether the bus voltage is greater than or equal to a first preset voltage threshold comprises: The judgment is made according to the following formula: U0≥βU N Among them, U0 represents the bus voltage, β represents a constant, which is 5%-15%, and U N Indicates the rated voltage of the busbar.
7. A distribution network evaluation system based on zero-sequence current feature extraction, characterized in that: The system comprises: A zero-sequence current acquisition module is used to obtain the bus voltage and the zero-sequence current of each outgoing line in the target distribution network, and determine whether the preset line selection condition is met according to the bus voltage; A signal extraction module is used to perform wavelet multi-resolution decomposition on the zero-sequence current of each outgoing line and extract transient characteristic signals if the preset line selection conditions are met. The transient characteristic signals include a DC signal component, an industrial frequency signal component, and a high-frequency oscillation component; An energy calculation module, used for obtaining the non-power frequency energy of the corresponding line according to the DC signal component and the high-frequency oscillation component; An energy ratio acquisition module is used to traverse the non-power frequency energy of each line to obtain the energy ratio of the non-power frequency energy of any line to the total non-power frequency energy of all lines in the target distribution network; The fault line location module is used to determine whether the energy ratio of each line is greater than a preset ratio threshold. If it is greater than the preset ratio threshold, the corresponding line is a fault line.
8. The distribution network evaluation system based on zero-sequence current feature extraction according to claim 7 is characterized in that: The signal extraction module is also used for: Accumulating and reconstructing the DC signal component and the high-frequency oscillation component to obtain a non-industrial frequency signal; The non-power frequency signal is subjected to Hilbert transformation to obtain the instantaneous amplitude of the non-power frequency signal, and the non-power frequency energy of the non-power frequency signal is calculated according to the instantaneous amplitude.
9. A storage medium, characterized in that: include: The storage medium stores one or more programs, which, when executed by a processor, implement the distribution network evaluation method based on zero-sequence current feature extraction as described in any one of claims 1-6.
10. An electronic device, characterized in that: The electronic device comprises a memory and a processor, wherein: The memory is used to store computer programs; When the processor is used to execute the computer program stored in the memory, it implements the distribution network evaluation method based on zero-sequence current feature extraction described in any one of claims 1-6.